Euro 6 Diesel Cars Emit NOx At Double Rate Of Modern Trucks & Buses

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In another example of the disparity between the reality of diesel cars and common sales claims, the independent research organization known as the International Council on Clean Transportation has revealed in a new paper that Euro 6 diesel passenger cars emit NOx at over double the rates that modern Euro VI buses and trucks do (on average).

The put that more plainly, the International Council on Clean Transportation (ICCT) paper noted that “the average amount of NOx present in exhaust emissions from modern diesel passenger cars under real-world conditions is more than double the levels from modern trucks and buses.”

The figures are the result of data obtained from 24 Euro VI buses and trucks through the use of a chassis dynamometer (by the Technical Research Centre of Finland) and through on-road testing with portable emissions testing equipment (by the German type-approval agency KBA).

Green Car Congress provides more:

“On average, NOx emissions of the heavy-duty vehicles tested were approximately 210 mg/km. Currently, NOx emissions of Euro 6 diesel passenger cars under real-world driving conditions are approximately 500 mg/km, as determined by testing carried out by KBA and other European type-approval agencies. In addition, the average conformity factor — the ratio of the test result to the regulatory limit — for the heavy-duty engines was less than 1, meaning that on-road emissions stayed below the Euro VI engine type-approval test limits.

“Further, CO2 emissions — which are proportional to fuel consumption — for heavy-duty vehicles are roughly 5 times those of cars. In other words, on an engine-load basis, heavy-duty vehicles are about 10 times better than light-duty diesels at reducing NOx.

“The differences are attributable in large part to differences in how light-duty and heavy-duty vehicle emissions are regulated, according to Rachel Muncrief, ICCT researcher and author of the paper. Significant real-world emissions and conformity-factor reductions were accomplished in the transition from Euro V to Euro VI heavy-duty vehicle standards.”

These reductions were primarily the result of: the inclusion of an off-cycle test during the type approval; improved test cycle (cold start + lower load conditions, and transient + higher load conditions); and “PEMS test for in-service conformity testing, with limited restrictions on the boundary conditions used during the test and subsequent data processing.”

The current Euro 6 regulation for diesel passenger cars includes none of these Euro V to Euro VI changes. Hence the disparity.

“The contrasting performance highlights the importance of an upcoming decision on strengthening the real-driving emissions (RDE) test for passenger cars in the EU,” the ICCT noted.

“The significantly lower NOx emission levels of trucks and buses are most likely a result of differences in regulation. Official testing requirements of light-duty vehicles remain limited to laboratory measurements of carefully prepared prototype vehicles.”

The Managing Director of ICCT in Europe, Dr Peter Mock, stated:  “In contrast, for measurement of NOx emissions from trucks and buses, mobile testing devices became mandatory in 2013. As a consequence, randomly selected vehicles can be tested under real-world driving.”

While things are set to improve somewhat with the impending implementation of the European Real-Driving Emissions regulation, there is still currently a lot of room for manufacturers to game the system.

For instance, for some reason, the new regulation will allow manufacturers to choose special prototype cars for “real-world” emissions testing rather than simply doing real-world testing on vehicles that had actually been sold to customers (ideally, randomly selected vehicles). Who does that plan make sense to? That obviously isn’t actual “real-world” testing, is it?

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James Ayre

James Ayre's background is predominantly in geopolitics and history, but he has an obsessive interest in pretty much everything. After an early life spent in the Imperial Free City of Dortmund, James followed the river Ruhr to Cofbuokheim, where he attended the University of Astnide. And where he also briefly considered entering the coal mining business. He currently writes for a living, on a broad variety of subjects, ranging from science, to politics, to military history, to renewable energy.

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